1. Field of the Invention
The present invention relates to an image display apparatus that displays a series of intra-subject images, which are picked up in time sequence.
2. Description of the Related Art
In recent years, in the endoscope field, there has been proposed a swallow-type capsule endoscope provided with an imaging function and a radio communication function, and a capsule endoscope system that acquires intra-subject images using this capsule endoscope has been developed. This capsule endoscope operates so as to move through a body cavity, for example, the inside of organs such as stomach and small intestine according to its peristaltic movement and pick up intra-subject images, for example, every 0.5 second in a period after the endoscope is swallowed for observation (examination) from a mouth of a subject until it is naturally discharged.
While the capsule endoscope is moving inside of the subject, the images picked up by this capsule endoscope are sequentially transmitted to an external receiving apparatus via radio communication. The receiving apparatus has a radio communication function and a memory function, so that the images received from the capsule endoscope inside the subject are sequentially stored in a memory. The subject can freely act in the period after swallowing the capsule endoscope until naturally discharging it by carrying the receiving apparatus. After the capsule endoscope is naturally discharged from the subject, the images accumulated in the memory is loaded onto an image display apparatus by a doctor or a nurse, and the images of the organs inside the subject can be displayed on the image display apparatus to make a diagnosis for the subject (e.g., Japanese Patent Application Laid-Open No. 2003-19111).
Generally, such an image display apparatus sequentially displays a series of intra-subject images picked up by the capsule endoscope, and displays a time bar indicating an elapsed time from imaging start of the series of images. By confirming this time bar, the doctor or the nurse knows the elapsed time from the imaging start until the intra-subject image being displayed was picked up. In this case, the doctor or the nurse, based on the elapsed time, estimates a position of the capsule endoscope moving inside the subject until the intra-subject image being displayed was picked up, that is, an imaged region (organ) of the intra-subject image being displayed. Also, there is an image display apparatus that detects average colors of respective images contained in a series of intra-subject images and further displays the detected average colors of the respective images on the above-described time bar. In this case, the average colors of the intra-subject images are unique to the respective intra-subject regions, and are displayed in areas on the time bar temporally corresponding to the respective intra-subject images, so that the doctor or the nurse estimates the imaged region (organ) of the intra-subject image being displayed by visually confirming the average color displayed on the time bar.
However, the above-described conventional image display apparatus has a problem in that since the average colors of the respective intra-subject images are displayed on the time bar to color-code the time bar by the intra-subject region, in many cases, borders between the adjacent displayed colors on the time bar are unclear, which makes it difficult to know the border between the images when the intra-subject region changes (e.g., border between the images at the time of change from an image of stomach to an image of small intestine) in a series of intra-subject images, and thus makes it difficult to determine the intra-subject region whose image is displayed. This problem is remarkable in the images in temporal vicinity of the borders of the images.